In fiscal 2012, 99.3% of waste concrete lumps were recycled. The 2014 Construction Recycling Promotion Plan drawn up by the MLIT set a goal for fiscal 2018 of maintaining this already high level of 99%. The main use of recycled concrete lumps is as material for roadbed. In metropolitan areas there are concerns that regenerated crusher-run could accumulate due to the increasing amounts of waste concrete. Therefore, to maintain the recycling ratio, the use of waste concrete as a material for new concrete needs to be increased.
Under the assumption that concrete made with recycled aggregate is to be used for civil structures, this study aims to suggest reasonable quality standards for recycled aggregate and quality control methods.
<Examination on measures against the drying shrinkage of recycled aggregate>
Regarding how the quality of recycled aggregate, such as its water absorption rate, affects drying shrinkage, this study conducts drying shrinkage tests and crack tests on restricted concrete with the purpose of suggesting categories of structures for which recycled aggregate can be used based on the degree of shrinkage and the scope of application of expansive admixtures as measures against drying shrinkage.
<Examination of a quality control method for aggregate mixed with recycled materials>
This study is being conducted in cooperation with the Innovative Materials and Resources Research Center (iMaRRC) in Tsukuba. The purpose is to suggest quality standards for concrete made with recycled aggregate under expected uses. The following will be examined and results of those examinations will be compiled: ASR control measures when recycled aggregate is used, measures against drying shrinkage, the use of recycled fine aggregate and the effects of quality variations.